..... other than trying to extend sovereignty, is to set up a SOSUS-like system so they can protect that Hainan base, keep out our attack boats and turn the S. China Sea into a SLBM bastion from which to safely launch their missiles. Interesting strategic problem.
Here is an overhead view of the port and underground sub pen on Hainan Island discussed earlier. Quite a complex and quite an investment. Meant to utterly dominate that area and, in my mind, provide three other important benefits - Sits astride the oil sea lanes to Taiwan and Japan. Provides a protected first and second strike capability vis-a-vis India without missile plumes/tracks emanating from north China that would make US/Russia very nervous. And holds at risk all forward US/allied Pacific assets to include Hawaii, Australia and Okinawa/Guam, et al.
SLBM's would likely not have the legs for a shooting match with the US mainland (that's the job of an esimated 3,000 miles of underground ICBM launch tunnels farther north. Falls right in line with their anti access / area denial strategy. Very destabilizing and we're falling behind the curve. Time to wake up.